1. Field
Embodiment of the present invention relate to oxide semiconductor devices, methods of manufacturing oxide semiconductor devices, display devices having oxide semiconductor devices, and methods of manufacturing display devices including oxide semiconductor devices. More particularly, embodiments relate to oxide semiconductor devices including gate insulation layers having recess structures, methods of manufacturing the oxide semiconductor devices including the gate insulation layers having the recess structures, display devices including the oxide semiconductor devices, and methods of manufacturing display devices having the oxide semiconductor devices.
2. Description of Related Art
A conventional bottom gate type thin film transistor (TFT) includes a gate electrode disposed on a substrate, a gate insulation layer located on the gate electrode, a source electrode and a drain electrode positioned on the gate insulation layer, and an active layer contacting the source and drain electrodes and the gate insulation layer between the source and drain electrodes.
In manufacturing the conventional bottom gate type thin film transistor, a metal layer is formed on the gate insulation layer to form the source electrode and the drain electrode, and an internal stress may be generated in the gate insulation layer while forming the metal layer on the gate insulation layer. When an active layer is formed on a gate insulation layer having internal stress, voltage-current characteristics of the transistor may be deteriorated. Additionally, etching damage is easily generated on a surface of the gate insulation layer while patterning the metal layer for forming the source and drain electrodes. Furthermore, the gate insulation layer is frequently contaminated by etching such as metal compounds and metallic particles generated in an etching process for the metal layer. Thus, an interface between the active layer and the gate insulation layer may be irregular, thereby deteriorating electrical characteristics of the transistor. For example, the transistor may have poor electrical characteristics such as increased variation of threshold voltages (Vth), decreased charge mobility, reduced operation current (Ion), etc. When an oxide semiconductor device includes a gate insulation layer having an internal stress, etching damage, and/or etching by-products remaining thereon, the oxide semiconductor device may have deteriorated electrical characteristics, such that the oxide semiconductor devices having the deteriorated electrical characteristics may not be suitable for use in display devices such as a liquid crystal display (LCD) device or an organic light emitting display (OLED) device.